Studies on wear resistance of PTFE filled with glass and bronze particles based on Taguchi technique

An attempt has been made to study the influence of wear parameters like applied load, sliding speed, sliding distance on the dry sliding wear of polytetrafluroethylene (PTFE), PTFE + 25% glass and PTFE + 40% bronze composites. Experiments, based on the techniques of Taguchi, were performed to acquire data in a controlled way. An orthogonal array and the analysis of variance were employed to investigate the influence of process parameters on the wear of composites. The worn surfaces were examined using scanning electron microscope (SEM). The experimental results show that sliding distance and applied load were found to be the more significant factors among the other control factors on wear. The objective is to establish a correlation between dry sliding wear of composites and wear parameters. These correlations were obtained by multiple regressions. A good agreement between the predicted and actual wear resistance was seen

INFLUENCE OF FIBRE VOLUME REINFORCEMENT IN DRILLING GFRP LAMINATES

This paper presents an investigation on the influence of fiber volume reinforcement on various aspects of machining. Drilling experiments were conducted to study the tool wear, surface finish, delamination factor and hole quality on GFRP composites. The work reports the variation of tool wear, surface roughness, hole quality, chip characteristics, delamination factor with the variation of fibre volume reinforcement. Results revealed that the increase in fiber percentage increased the tool wear, delamination factor, surface roughness value and decreased hole quality. Minimum surface roughness, tool wear and better hole quality was obtained for 30% fibre content composites. 70% Fibre content composites produced hazardous surface roughness. Pull out of fibres and fibril formation are significant in decreasing the hole quality and increased surface roughness. Increased tool – fibre interaction and thermal softening of the tool causes increased tool wear. In higher fibre content composites, extensive plasticity was absent consequently brittle ceramic fibres were fractured easily. Hence small segment type chips were obtained. The fibre pull out and fibrils present near the hole exit forms the remainder of the laminate causes increased damage zone near the hole exit. Hence high delamination factor was obtained

Cyclotron activated nanoparticles: application in PET/SPECT imaging

Introduction: Nanoparticles (NP) are widely used in everyday life. Pigments, cosmetic products, some foods, suncream, and many other products may contain NPs, and possible environmental pollution may be associated with wastes and NP release. Investigation of possible toxicological effects from exposure to NPs requires in vivo bio-distribution studies. Three frequently applied NPs: silver (Ag), zinc oxide (ZnO) and titanium dioxide (TiO2) were tested by our research group in activated form for quantification and tomographic detection using PET and SPECT. Materials and Methods: Activated NPs were produced in the JRC Cyclotron (Scanditronix MC40). Dry NP powders were placed in sample holders and activated for several hours by proton or deuterium irradiation. The resulting target material was left to decay for 2 weeks to allow irrelevant short-lived isotopes to decay away. Ag-105 (Ag-NP), Zn-65 (ZnO-NP) and V-48 (TiO2-NP) isotopic purity and radioactivity were determined precisely with gamma spectroscopy (Canberra GX2518 HPGe) using Genie 2000 software. The data were used to adjust quantification factors for imaging instruments NanoSPECT/CTPlus (Mediso Ltd.) and nanoScan PET/MRI (Mediso Ltd.). Using SPECT several peaks of the different gamma photon energies characteristic of the specific isotope spectra were applied. We detected 64.0, 280.5, 443.4 and 344.5 keV peaks for Ag-105, and the 560 keV peak for V-48 in addition to detecting the 511 keV annihilation peak of Zn-65 for PET. The HiSPECT (SciVis Gmbh, Germany) reconstruction algorithm was used to calculate volumes from multiplexing overlapping multi-pinhole SPECT while Tera-Tomo (Mediso Ltd) 2-D and 3-D iterative reconstruction algorithms were used to calculate PET volumes. Results: The specific activity of all the NP types used was between 1-1.5 MBq/mg. The radiation emission of Zn-65 was detected using PET, Ag-105 and V-48 were detected with both PET and SPECT. All nanoparticle samples have shown adequate signal-to-noise ratio in their spectral properties for SPECT (Ag-105, V-48) and PET (Ag-105, Zn-65 and V-48) imaging in durations between 40 minutes and 120 minutes of signal integration. Conclusion: All PET and SPECT imaging data were capable of determining the original radioactivity and distribution of the nanoparticles. Quantitation error was 24,3%. These findings provide the basis for the application of non-conventional long-lived isotope tracking of nanoparticles. The actual practicality and usefulness of the technique at realistic NP doses and at lower doses in various organs after biodistribution still has to be studied. Acknowledgement. This study was in part supported by EC-FP7 Transnational Access Facilities grant QNANO.JRC.I.4-Nanobioscience